Title: Nondispersing wave packets

Abstract

A nondispersing Rydberg wave packet can be made by applying a weak, linearly polarized field at the Kepler frequency of a Rydberg atom. The field phase locks the electron's motion to the microwave field, and the wave packet retains its spatial localization for times in excess of a microsecond. The electron's orbital oscillation leads to an oscillating dipole, which can either oscillate in phase or out of phase with the applied microwave field, creating wave packets analogous to Trojan and anti-Trojan wave packets described theoretically. Our observations can be described in both quantum mechanical and classical terms.

@article{osti_20982358,
title = {Nondispersing wave packets},
author = {Maeda, H. and Gallagher, T. F.},
abstractNote = {A nondispersing Rydberg wave packet can be made by applying a weak, linearly polarized field at the Kepler frequency of a Rydberg atom. The field phase locks the electron's motion to the microwave field, and the wave packet retains its spatial localization for times in excess of a microsecond. The electron's orbital oscillation leads to an oscillating dipole, which can either oscillate in phase or out of phase with the applied microwave field, creating wave packets analogous to Trojan and anti-Trojan wave packets described theoretically. Our observations can be described in both quantum mechanical and classical terms.},
doi = {10.1103/PHYSREVA.75.033410},
journal = {Physical Review. A},
number = 3,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}

We show how an external field can modify wave packet dynamics in two-electron atoms. The method provides a realistic scheme for creating nondispersing, slowly decaying radial wave packets. An analogy with mode locking in lasers and the idea of a quantum shutter are discussed.

Long-lived, nondispersing circular, or Bohr, wave packets are produced starting from Li Rydberg atoms by exposing them first to a linearly polarized microwave field at the orbital frequency, 17.6 GHz at principal quantum number n=72, which locks the electron's motion into an approximately linear orbit in which the electron oscillates in phase with the microwave field. The microwave polarization is changed to circular polarization slowly compared to the orbital frequency, and the electron's motion follows, resulting in a nondispersing Bohr wave packet.

The observation of an atomic wave packet by use of a coherent, nonlinear-optical process is reported. Wave packets formed in K or Rb vapor by two-photon excitation of ns and (n{minus}2)d states (n=8 for K; n=11 , 12 for Rb) with red ({approximately}620{minus}nm) , 80{endash}100-fs pulses were detected by four-wave mixing in pump-probe experiments. The temporal behavior of the wave packet is observed by monitoring the coherent UV radiation generated near the alkali mp {sup 2}P {r_arrow} {sup 2}S{sub 1/2} (7{le}m{le}12 for Rb; 5{le}m{le}7 for K) resonance transitions when a probe pulse is scattered by the wave packet established bymore » the earlier (identical) pump pulse. The spatial and spectral characteristics of the UV emission are well described by axially phase-matched four-wave mixing, and all the prominent frequency components of the wave packets are associated with energy differences between pairs of excited states for which {Delta}l=0 or {Delta}l=2 . These results demonstrate that the wave packet modulates {chi}{sup (3)} of the medium, thus rendering the wave packet detectable. {copyright} {ital 1998} {ital Optical Society of America}« less